Wednesday, July 29, 2009

Capstan rope winch

The white object to the left in the photo below is a capstan rope winch; a motor with a rotating cylinder that pulls a rope with a winch-like action. The rope wraps a couple of times around the capstan and when slight tension is applied to the free end of the rope, friction takes over and begins pulling on the load end of the rope. When tension is relaxed on the free end, the rope slips on the capstan and the load waits. The length of rope used on the capstan is unlimited. That's the beauty of the capstan rope winch over a fixed drum winch. Winches are limited by the length of cable that can be conveniently stored on an attached spool. With a capstan, the free end of rope accumulates on the ground or in a bucket.

This capstan is powered by a 12 volt car battery and includes a thermal circuit breaker, solenoid, and foot-operated switch (not visible in photo above) so both hands are free to handle the rope. It is rated to pull up to 1000 pounds and will lift 500 pounds at 31 feet per minute...about 6 inches per second. Not too fast and not too slow.

I'm only planning to lift, at most 300 pounds, up a 35 degree inclined plane, using a cart with rollers on a 2x6 rail, about 150 linear feet. I estimate about 2.5 to 3 minutes of travel time for the load I'll be lifting.

A plywood box covers and protects the wiring components and the foot switch nestles alongside the battery on the platform when not in use.

The carriage is a pair of steel rails onto which a pair of wheels are axled, and a platform of hardwood to which the capstan is bolted. The steel rails form handles like a wheel barrow to help position the tool, and a steel wire-rope cable is attached with carabiners so that it can be wrapped around a large tree to anchor it against the load.

What load? Granite rock, what else?!

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